Engine architecture using electric machine

ABSTRACT

There is described a method for controlling an engine and a system architecture for an engine. The system architecture comprises a first electric machine having a single rotor dual stator configuration for operating as a starter-generator for the engine; a second electric machine having a single rotor dual stator configuration for operating as a motor; a dual channel motor drive unit coupled to the second electric machine; a dual channel power control unit coupled to the first electric machine and the motor drive unit; a dual channel full authority digital engine control (FADEC) coupled to the dual channel power control unit and the dual channel motor drive unit; and at least two accessories coupled to the second electric machine and driven by motive power from the single rotor of the second electric machine.

TECHNICAL FIELD

The application relates generally to engine architectures and moreparticularly, to designs incorporating electric machines such asalternators and motors.

BACKGROUND OF THE ART

The demand for electrical power onboard modern aircrafts is increasing.New avionic equipment and more onboard entertainment systems also needmore power. With more power generation capability in the engines, thetrend is to unify the on board power systems to electrical power only,eliminating pneumatic and hydraulic power systems. The operation ofengine accessories using electrical power may also have its advantages.Reliability and health monitoring when dual redundant electrical systemscan be implemented is a prime advantage of electrically driven systemswhich may be more weight and cost effective than with other types ofpower systems. Therefore, there is a need for continued improvements tothe design of dual redundant systems using electric machines.

SUMMARY

In one aspect, there is provided a gas turbine engine comprising: afirst electric machine having a single rotor dual stator configurationfor operating as a starter-generator for the engine; a second electricmachine having a single rotor dual stator configuration for operating asa motor; a dual channel motor drive unit coupled to the second electricmachine; a dual channel power control unit coupled to the first electricmachine and the motor drive unit; a dual channel full authority digitalengine control (FADEC) coupled to the dual channel power control unitand the dual channel motor drive unit; and at least two accessoriescoupled to the second electric machine and driven by motive power fromthe single rotor of the second electric machine.

In another aspect, there is provided a method of controlling an engine,the method comprising: operating a first rotor in a first electricmachine having a single rotor dual stator configuration to rotate thefirst rotor and thereby start the engine; once the engine is started,providing a first power source and a second power source from aninteraction of a magnetic field of the first rotor with the dual statorin the first electric machine; channeling the first power source towardsa second electric machine having a single rotor dual statorconfiguration via a dual channel power control unit and a dual channelmotor drive unit; channeling the second power source towards the secondelectric machine independently from the first power source via the dualchannel power control unit and the dual channel motor drive unit; anddriving at least two independent accessories by applying the first powersource and the second power source to a second rotor of the secondelectric machine via the single rotor dual stator configuration.

In yet another aspect, there is provided an oil and fuel control systemfor an engine, the system comprising: an electric machine having asingle rotor coupled to a dual channel stator comprising a first statorand a second stator, for operating as a motor to generate motive power;a dual channel motor drive unit coupled to the electric machine; a dualchannel full authority digital engine control (FADEC) coupled to thedual channel motor drive unit; an oil delivery system comprising an oilpump and oil accessories, coupled to the single rotor of the electricmachine; and a fuel delivery system comprising a fuel pump and fuelaccessories, coupled to the single rotor of the electric machine. Thefuel delivery system may be a demand fuel system which is controlled bythe speed of the motor.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 shows a schematic cross-sectional view of an example of a gasturbine engine with an electric machine integrated therein;

FIG. 2 is a schematic radial cross-sectional view of another example ofan electric machine;

FIG. 3 is a block diagram of an exemplary system architecture using thetwo dual electric machines;

FIG. 4 is a block diagram of an exemplary embodiment for a fuel and oilcontrol system; and

FIG. 5 is a flowchart of an exemplary method for controlling an enginewith a system architecture as per FIGS. 3 and 4.

DETAILED DESCRIPTION

There is described herein a system architecture for incorporating intoan engine. FIG. 1 illustrates an exemplary gas turbine (GT) engine. Anelectric machine 10 driven by a shaft 5 operates within the gas turbineengine. Although the illustrated gas turbine engine is a turbofan, thesystem as described herein can be employed with a turboprop engine or aturboshaft engine and is not limited to application on aircraft engines.The engine may be an aircraft engine, a ship engine, a vehicle engine,etc. In alternative embodiments, the electric machine 10 may be providedin other types of engines, such as an electric engine and amore-electric engine.

The electric machine 10 is operable as either a motor or a generator, orboth, depending on the associated control provided. The materials forthe machine 10 may be any deemed suitable by the designer. Someexemplary materials are samarium cobalt permanent magnets, copper powerand control windings, a suitable saturable electromagnetic material(s)for the stator teeth and power and control flux buses, such as Hiperco50 alloy (a trademark of Carpenter Technology Corporation) may be used,although other suitable materials, such as electrical silicon steelscommonly used in the construction of electromagnetic machines, may alsobe used. The rotor can be ferromagnetic, electromagnetic or a permanentmagnet, and may be provided in an outside or inside configuration, orany other suitable configuration. The stator teeth, power and controlflux buses may be integral or non-integral with one another, as desired.

While machine 10 may have any suitable configuration, in this example itis illustratively a permanent magnet electric machine. FIG. 2 shows anexample of an electric machine 100 described in U.S. Pat. No. 7,262,539,incorporated herein by reference, having two independent channelsections which in essence provide two separately controllable machines,namely machine A and machine B, within the same stator structure 102.The rotor 104 is shown as being outside the stator 102, but it can beinside if desired. Briefly, the stator 102 has a plurality of statorwindings 106 provided in slots 108 of stator 102. Permanent magnets 110are provided on the rotor 104. The channels A, B comprise independentand separated sets of windings 106, and thus machine 100 has atwo-in-one electric machine design. The windings of channel A areconfined to the sector of the stator indicated as “A” in FIG. 2, whilethe windings of channel B are confined to the sector of the statorindicated as “B” in FIG. 2. The windings are independently operable by acontroller, and may be operated each in a motor and generator mode. Forexample, rotation of rotor 104 may be used to generate electricity inthe windings 106 of channel A, while the windings of channel B areturned “off” via the control coils 107 effect on the magnetic propertiesof the stator sector. Alternately, the windings of channel B may also beturned “on” and also used to generate electricity in tandem with thewindings of channel A. The control of the relevant stator, using DCcurrent in the control winding is useful for both controlling thegenerator mode of the machine and the motor mode of the machine. In thegenerator mode of the machine, the DC control current controls the ACoutput current from the windings as is described in U.S. Pat. No.7,262,539. In the motor mode, the control current is normally held at afixed value unless a fault is detected in either the relevant motorwinding or in the relevant motor drive circuit, at which point thecontrol current would be set to zero and the relevant motor drive wouldbe shut off, preventing current generated by the continued rotation ofthe machine from circulating in the fault circuit. The non-failedmotor/motor drive channel is used to continue the rotation of themachine to drive the accessories, while repairs/replacement would bemade at the next earliest opportunity.

Turning now to FIG. 3, there is illustrated an exemplary systemarchitecture 200 for an engine incorporating the electric machine 10described above. In this example, the electric machine 10 operates as astarter-generator 210 and comprises a single rotor 201 dual stator 203configuration. The starter-generator 210 is used for starting the engineand also generating electricity when the engine is in operation. Twoseparate sets of stator windings (Stator A, Stator B) 203 are used todrive a common rotor 201. The two stators 203 each output electricityvia their respective sets of windings during the generation mode ofoperation.

The dual channel single rotor starter-generator 210 is controlled by adual channel full authority digital engine control (FADEC) 206 via adual channel power control unit (PCU A, PCU B) 202. The FADEC 206 maycomprise an electronic engine controller (EEC) or engine control unit(ECU) and its related accessories in order to control all aspects ofengine starting performance. In particular, the dual FADEC 206 controlsthe input current to both starter channels of the starter-generator 210based on any one of a number of input parameters, such as speed,temperature, altitude, and forward speed.

In the embodiment as illustrated, the electric machine 10 also operatesas a motor 212 and comprises a single rotor 201 dual stator 203configuration. The dual stator is powered via a dual motor drive 211.The single rotor 201 of the motor 212 is coupled to two or moreaccessories 208. The dual channel single rotor motor 204 is alsocontrolled by the dual channel FADEC 206 via the dual motor drive unit211. In some embodiments, the single rotor 201 of the motor 212 may beused to drive at least two accessories, such as an oil pump, a fuelpump, a hydraulic pump, etc. This architecture removes severalcomponents from the system, such as an additional dual motor and relateddual drive system. This improves the overall weight of the system andenhances reliability. The high reliability of the dual electricallydriven accessories 208 is achieved by the dual power control unit 202and dual stators 203 of the starter-generator 210 and the dual motordrive in conjunction with dual stators of the motor 212, while theestablished high reliability of mechanical rotating machines iscapitalized on using a single rotor 201 in both the starter-generator210 and the motor 212.

In some embodiments, two of the accessories 208 coupled to the motor 212are an oil delivery system 216 and a fuel delivery system 218. FIG. 4illustrates a fuel and oil control system 214 as may be used in thesystem 200 of FIG. 3 in combination with the starter-generator 210 anddual PCU unit 202. Alternatively, control system 214 may be providedindependently therefrom in combination with another system configurationand with a plurality of different engine types.

The single rotor 201 of the motor 212 may drive both the oil pump of theoil delivery system 216 and the fuel pump of the fuel delivery system218 since they require high torque at different times. At high speed(high flow), the fuel pump requires high torque, whereas at low speedthe torque is not required for fuel pumping. Cold starting oil pumpsrequire high torque initially and this need diminishes as the oiltemperature reaches normal operating temperature, before requiring thetorque for the fuel pump operation at high speed.

Referring back to FIG. 3, once the engine has been started, the dualstators 203 in the generator 210, in combination with the dual powercontrol unit 202, provide redundant power to the dual channel singlerotor drive motor 212, which provides motive power to the fuel deliverysystem 218 and the oil delivery system 216 via the single rotor 201 ofthe motor 212. The fuel flow may be controlled by controlling the speedof the fuel pump in the fuel delivery system 218 by the dual FADEC 206and/or dual PCU 202, and the oil delivery thus becomes a function of thefuel flow rather than the gas generator speed. Since oil is primarilyrequired for heat removal and heat generation is a strong function offuel flow, a single dual motor 212 may be used for both oil delivery andfuel delivery. Thus the size of motor required for the oil pump wouldalso be required for the fuel pump, but because the torque duty for eachof these systems is asymmetrically complimentary, the requirement forboth pumps can be fulfilled with a single motor and drive system. Sincethis removes many components from the system, the reliability is greatlyenhanced as is the overall system weight.

Note that although the electric machine 10 has been illustrated ashaving dual channels, it may also have more than two channels byproviding a single rotor rotating relative to multiple independentstators. In the case of dual channels, the rotor rotates relative to afirst “virtual” stator and also relative to a second “virtual” stator.The electric machine 10 is thus a “two-in-one” machine in this case. Theoutput of these two “machines” may then be combined, which permits theoption of operating the “two machines” as one. Electric machine 10 maythen be connected to fully redundant accessory systems. In a gas turbineintegrated starter-generator application, this dual- or multi-channeldesign permits a fully redundant system with a minimum of hardware,thereby minimizing weight and space and increasing reliability. As well,since generator efficiency is proportional to I² losses, it is oftendesirable to run two “machines” like this, each at ½ of the outputcurrent, rather than one machine at full output current. Further, powerfrom the two “machines” may be shared, if desired, between the PCUs 202with the appropriate connections, etc., to permit redundancy in the caseof a “machine” or PCU failure.

In some embodiments, the dual channel architecture as depicted in FIG. 3defines a first channel arrangement composed of the starter-generator210, the FADEC 206, the power control unit 202, the motor drive unit 211and the motor 212 that is electrically independent from a second channelarrangement composed of the starter-generator 210, the FADEC 206, thepower control unit 202, the motor drive unit 211 and the motor 212. Theindependence of the first channel from the second channel provides areduction in the probability of an in-flight shutdown of a propulsionengine so equipped. It also eliminates the possibility of engine shutdown due to a single electrical fault or a single point failure. Inaddition, the possibility of an inability to start the engine due to asingle component failure is also eliminated. In either case, i.e. duringan in-flight shut down or an inability to start, at least two unrelatedfaults would be required to cause such failures the probability if whichis considered as highly improbable.

The machine 10 may be single or multi-phase. The windings may havesingle or multi turns per slot, the number of turns of windings does nothave to equal the number of turns of control windings, the number ofturns of a winding does not necessarily have to be a whole number, thenumber of primary windings does not have to equal the number of controlwindings, as one or more windings in a slot may perhaps be present inanother slot. A variety of winding types may be used (squirrel cage,lap, etc.), and the windings may be any conductor(s) (i.e. singleconductor, more than one wire, insulated, laminated, etc.) or may besuperconductors. In multiphase machine, there may be zigzag, delta, orY-connected windings in accordance with known techniques. There need notbe an air gap between the primary and control winding, as long as thewindings are electrically isolated from one another.

FIG. 5 illustrates the method of controlling an engine using a systemarchitecture as described above. As depicted in FIG. 3, the systemcomprises a first electric machine with a single rotor dual statorconfiguration operating as a starter-generator. In a first step 220, therotor of the first electric machine is operated to rotate and therebystart the engine. Once the engine is started, the interaction of themagnetic field of the rotor in the first electric engine with the dualstator arrangement generates two separate power sources, a first powersource 222 and a second power source 224. The first power source ischanneled towards the second electric machine via a first channelarrangement composed of the dual channel power control unit and the dualchannel motor drive unit 226. The second power source is also channeledto the second electric machine via a second channel arrangement composedof the dual channel power control unit and the dual channel motor driveunit 228. The two independent power sources are used to drive at leasttwo independent accessories using the single rotor dual statorconfiguration of the second electric machine 230.

In some embodiments, the at least two independent accessories are a fueldelivery system and an oil delivery system, as depicted in FIG. 4. Thefuel delivery system may be driven by controlling the speed of deliveryof fuel from the fuel pump, and the oil delivery system may becontrolled as a function of the fuel delivery speed.

In some embodiments, control of the accessories is done by the dualFADEC 206 and/or the dual PCU 202. Thus, a first channel arrangementcomposed of the first electric machine, the FADEC, the power controlunit, the motor drive unit and the second electric machine may beelectrically independent from a second channel arrangement composed ofthe first electric machine, the FADEC, the power control unit, the motordrive unit and the second electric machine

While illustrated in block diagrams as groups of discrete componentscommunicating with each other via distinct data signal connections, itwill be understood by those skilled in the art that the presentembodiments may be provided by a combination of hardware and softwarecomponents, with some components being implemented by a given functionor operation of a hardware or software system, and some of the datapaths illustrated being implemented by data communication within acomputer application or operating system. For example, the power controlunits 202 may be implemented using hardwired logic, Field-ProgrammableGate Arrays (FPGAs), analog systems, etc. The structure illustrated isthus provided for efficiency of teaching of the present embodiment,which can be carried out as a method or embodied in a system. The abovedescription is meant to be exemplary only, and one skilled in the artwill recognize that changes may be made to the embodiments describedwithout departing from the scope of the invention disclosed.Modifications which fall within the scope of the present invention willbe apparent to those skilled in the art, in light of a review of thisdisclosure, and such modifications are intended to fall within theappended claims.

1. A gas turbine engine comprising: a first electric machine having asingle rotor dual stator configuration for operating as astarter-generator for the engine; a second electric machine having asingle rotor dual stator configuration for operating as a motor; a dualchannel motor drive unit coupled to the second electric machine; a dualchannel power control unit coupled to the first electric machine and themotor drive unit; a dual channel full authority digital engine control(FADEC) coupled to the dual channel power control unit and the dualchannel motor drive unit; and at least two accessories coupled to thesecond electric machine and driven by motive power from the single rotorof the second electric machine.
 2. The engine of claim 1, wherein afirst channel arrangement composed of the first electric machine, theFADEC, the dual channel power control unit, the dual channel motor driveunit and the second electric machine is electrically independent from asecond channel arrangement composed of the first electric machine, theFADEC, the dual channel power control unit, the dual channel motor driveunit and the second electric machine.
 3. The engine of claim 1, whereinat least one of the first electric machine and the second electricmachine is a regulated permanent magnet starter-generator.
 4. The engineof claim 1, wherein the engine is one of an electric engine and amore-electric engine.
 5. The engine of claim 1, wherein the firstelectric machine is coupled to a shaft of the gas turbine engine.
 6. Theengine of claim 1, wherein the at least two accessories are a fueldelivery system and an oil delivery system.
 7. A method of controllingan engine, the method comprising: operating a first rotor in a firstelectric machine having a single rotor dual stator configuration torotate the first rotor and thereby start the engine; once the engine isstarted, providing a first power source and a second power source froman interaction of a magnetic field of the first rotor with the dualstator in the first electric machine; channeling the first power sourcetowards a second electric machine having a single rotor dual statorconfiguration via a dual channel power control unit and a dual channelmotor drive unit; channeling the second power source towards the secondelectric machine independently from the first power source via the dualchannel power control unit and the dual channel motor drive unit; anddriving at least two independent accessories by applying the first powersource and the second power source to a second rotor of the secondelectric machine via the single rotor dual stator configuration.
 8. Themethod of claim 7, wherein driving the at least two independentaccessories comprises driving a fuel delivery system and an oil deliverysystem from the second rotor of the second electric machine.
 9. Themethod of claim 7, wherein driving the fuel delivery system and the oildelivery system comprises controlling a speed of delivery of fuel from afuel pump in the fuel delivery system, and controlling oil delivery as afunction of fuel delivery speed.
 10. The method of claim 7, furthercomprising controlling the first electric machine and the secondelectric machine with a dual channel full authority digital enginecontrol (FADEC).
 11. The method of claim 10, wherein controlling thefirst electric machine and the second electric machine with the FADECcomprises effecting control via the dual channel power control unit andthe dual channel motor drive unit.
 12. The method of claim 11, wherein afirst channel arrangement composed of the first electric machine, theFADEC, the dual channel power control unit, the dual channel motor driveunit and the second electric machine is electrically independent from asecond channel arrangement composed of the first electric machine, theFADEC, the dual channel power control unit, the dual channel motor driveunit and the second electric machine.
 13. An oil and fuel control systemfor an engine, the system comprising: an electric machine having asingle rotor coupled to a dual channel stator comprising a first statorand a second stator, for operating as a motor to generate motive power;a dual channel motor drive unit coupled to the electric machine; a dualchannel full authority digital engine control (FADEC) coupled to thedual channel motor drive unit; an oil delivery system comprising an oilpump and oil accessories, coupled to the single rotor of the electricmachine; and a fuel delivery system comprising a fuel pump and fuelaccessories, coupled to the single rotor of the electric machine. 14.The oil and fuel control system of claim 13, wherein the first stator iselectrically independent from the second stator.
 15. The oil and fuelcontrol system of claim 13, further comprising a dual channel powercontrol unit adapted to modulate an amount of torque provided to thefuel pump and the oil pump as a function of a fuel delivery speed.